supplementary materials

trans-Bis(acridine-N)dichloridopalladium(II)

In the title complex, [PdCl2(C13H9N)2], the PdII ion is four-coordinated in an essentially square-planar environment by two N atoms from two acridine ligands and two Cl- anions. The Pd atom is located on an inversion centre, and thus the asymmetric unit contains one half of the complex and the PdN2Cl2 unit is exactly planar. The dihedral angle between the PdN2Cl2 unit and the acridine ligand is 84.66 (6)°. In the crystal, the complex molecules are stacked in columns along the a axis connected by C-HCl hydrogen bonds, forming chains along [110]. In the columns, numerous intermolecular - interactions between the six-membered rings are present, the shortest ring centroid-centroid distance being 3.722 (4) Å.

In the title complex, [PdCl2(acr)2] (acr = acridine, C13H9N), the PdII
ion is four-coordinated in an essentially square-planar environment by two N
atoms from two acridine (acr) ligands and two Cl- anions (Fig. 1 and Table
1). The complex and the iodo analogue [PdI2(acr)2] crystallized in the
triclinic space group P1, whereas the analogous bromo Pd(II) complex
[PdBr2(acr)2] crystallized in the monoclinic space group
C2/c (Ha, 2010a,b).

The Pd atom is located on an inversion centre, and thus the asymmetric unit
contains one half of the complex and the PdN2Cl2 unit is exactly plane.
The nearly planar acridine ligands, with a maximum deviation of 0.033 (4) Å
from the least-squares plane, are parallel. The dihedral angle between the
PdN2Cl2 unit and acridine ligand is 84.66 (6)°. The Cl atoms are in
trans conformation with respect to each other and almost perpendicular
to the acridine planes, with the bond angle N1—Pd1—Cl1 = 89.75 (12)°. In
the crystal, the complex molecules are stacked in columns along the a
axis and connected by C—H···Cl hydrogen bonds, forming chains along [110].
In the columns, numerous intermolecular π-π interactions between the
six-membered rings are present, the shortest ring centroid-centroid distance
being 3.722 (4) Å.

To a solution of Na2PdCl4 (0.2014 g, 0.685 mmol) in H2O (20 ml)
was added
acridine (0.2561 g, 1.429 mmol), and the mixture was refluxed for 7 h. The
precipitate was then separated by filtration, washed with acetone and pentane,
and dried at 50 °C, to give a yellow powder (0.3369 g). Crystals suitable for
X-ray analysis were obtained by slow evaporation from a CH3CN solution.

Fig. 1. The structure of the title complex, with displacement ellipsoids drawn
at the 50% probability level for non-H atoms. Unlabelled atoms are related to
the reference atoms by the (1 - x, 1 - y, -z) symmetry
transformation.

Fig. 2. View of the unit-cell contents of the title complex. Hydrogen-bond
interactions are drawn with dashed lines.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.